Ancient extinct alligator found in Thailand

A newly described ancient alligator found in Thailand is reported to be closely related to the Chinese alligator (Alligator sinensis).

Researchers described Alligator munensis from a near complete fossilised skull dating back to less than 230,000 years old. The newly found prehistoric crocodilian is named after the Mun River in Thailand near where it was uncovered.

It was described in a paper published in Scientific Reports

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The A. munensis skull was found in the Ban Si Liam locality of eastern Thailand in the Nakhon Ratchasima province.

Thailand would have looked different more than 200,000 years ago. In this period, toward the end of the Pleistocene, much of Southeast Asia had lost some of its dense forest, giving way to open savannah. It is in the last 100,000 years or so that the region’s dense tropical rainforests have returned.

The A. munensis specimen found would have been alive in a period immediately following the loss of some of Southeast Asia’s megafaunal species.

Among them were the elephant-like Stegodon (extinct by the end of the Pleistocene about 12,000 years ago); Earth’s largest ever ape, the three-metre tall, 200–300-kilogram Gigantopithecus (extinct roughly 350,000 years ago); and giant hyenas.

Around the time in prehistory when A. munensis lived, the first modern Homo sapiens emergedin eastern Africa. While human ancestor Homo erectus is believed to have migrated to Southeast Asia between 500,000 and one million years ago, modern humans didn’t make it to the region until 60,000–100,000 years ago.

The newly discovered ancient alligator was compared to 19 specimens including four extinct alligator species, as well as the modern American alligator (Alligator mississippiensis), Chinese alligator and the spectacled caiman (Caiman crocodilus).

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A. munensis has some unique skull features including a broad, short snout and a tall skull. The animal had fewer teeth than other species, and nostrils positioned further from the tip of the snout than is common among alligators.

It is similar, however, in some ways to the Chinese alligator. Both species exhibit small openings in the roof of the mouth, a ridge along the top of the skull and raised, bony ridges behind the nostrils.

The authors speculate that the two species shared a common ancestor in the lowlands of the Yangtze-Xi and Mekong-Chao Phraya river systems. They suggest that the rise of the Tibetan Plateau 23–5 million years ago led to the divergence of the two species.

Large tooth sockets toward the back of the jaw suggest that A. munensis was capable of crushing large shells. The authors propose that the animal specialised in eating hard-shelled prey such as snails in addition to other animals.